Showing papers by "Guy A. Rouleau published in 2013"
TL;DR: Empirical evidence of shared genetic etiology for psychiatric disorders can inform nosology and encourages the investigation of common pathophysiologies for related disorders.
Abstract: Most psychiatric disorders are moderately to highly heritable. The degree to which genetic variation is unique to individual disorders or shared across disorders is unclear. To examine shared genetic etiology, we use genome-wide genotype data from the Psychiatric Genomics Consortium (PGC) for cases and controls in schizophrenia, bipolar disorder, major depressive disorder, autism spectrum disorders (ASD) and attention-deficit/hyperactivity disorder (ADHD). We apply univariate and bivariate methods for the estimation of genetic variation within and covariation between disorders. SNPs explained 17-29% of the variance in liability. The genetic correlation calculated using common SNPs was high between schizophrenia and bipolar disorder (0.68 ± 0.04 s.e.), moderate between schizophrenia and major depressive disorder (0.43 ± 0.06 s.e.), bipolar disorder and major depressive disorder (0.47 ± 0.06 s.e.), and ADHD and major depressive disorder (0.32 ± 0.07 s.e.), low between schizophrenia and ASD (0.16 ± 0.06 s.e.) and non-significant for other pairs of disorders as well as between psychiatric disorders and the negative control of Crohn's disease. This empirical evidence of shared genetic etiology for psychiatric disorders can inform nosology and encourages the investigation of common pathophysiologies for related disorders.
2,058 citations
Dalhousie University1, Charité2, National Institutes of Health3, University of Geneva4, Karolinska Institutet5, State University of Campinas6, University of Adelaide7, University of Paris8, Medical University of Graz9, Mayo Clinic10, Academia Sinica11, University of Bonn12, University of Cagliari13, Johns Hopkins University14, French Institute of Health and Medical Research15, Ludwig Maximilian University of Munich16, Neuroscience Research Australia17, University of Toronto18, University of Göttingen19, Osaka University20, United States Department of Veterans Affairs21, University of California, San Diego22, University of Würzburg23, National Taiwan University24, Hokkaido University25, University of Antioquia26, University of Naples Federico II27, University of New South Wales28, Nagoya University29, Fujita Health University30, Harvard University31, Dresden University of Technology32, University of Iowa33, Université de Montréal34, University of Queensland35, Heidelberg University36
TL;DR: The key phenotypic measures of the “Retrospective Criteria of Long-Term Treatment Response in Research Subjects with Bipolar Disorder” scale currently used in the Consortium on lithium Genetics (ConLiGen) study are reported.
Abstract: OBJECTIVE: The assessment of response to lithium maintenance treatment in bipolar disorder (BD) is complicated by variable length of treatment, unpredictable clinical course, and often inconsistent compliance. Prospective and retrospective methods of assessment of lithium response have been proposed in the literature. In this study we report the key phenotypic measures of the "Retrospective Criteria of Long-Term Treatment Response in Research Subjects with Bipolar Disorder" scale currently used in the Consortium on Lithium Genetics (ConLiGen) study. MATERIALS AND METHODS: Twenty-nine ConLiGen sites took part in a two-stage case-vignette rating procedure to examine inter-rater agreement [Kappa (κ)] and reliability [intra-class correlation coefficient (ICC)] of lithium response. Annotated first-round vignettes and rating guidelines were circulated to expert research clinicians for training purposes between the two stages. Further, we analyzed the distributional properties of the treatment response scores available for 1,308 patients using mixture modeling. RESULTS: Substantial and moderate agreement was shown across sites in the first and second sets of vignettes (κ = 0.66 and κ = 0.54, respectively), without significant improvement from training. However, definition of response using the A score as a quantitative trait and selecting cases with B criteria of 4 or less showed an improvement between the two stages (ICC1 = 0.71 and ICC2 = 0.75, respectively). Mixture modeling of score distribution indicated three subpopulations (full responders, partial responders, non responders). CONCLUSIONS: We identified two definitions of lithium response, one dichotomous and the other continuous, with moderate to substantial inter-rater agreement and reliability. Accurate phenotypic measurement of lithium response is crucial for the ongoing ConLiGen pharmacogenomic study.
407 citations
University of Chicago1, Broad Institute2, University of Amsterdam3, Harvard University4, University of Queensland5, University of Toronto6, Vita-Salute San Raffaele University7, University of Antioquia8, Johns Hopkins University9, Yale University10, New York University11, Hofstra University12, University of Hong Kong13, University of São Paulo14, University of California, San Diego15, Université de Montréal16, University of Southern California17, University of Illinois at Chicago18, Ghent University19, University of Würzburg20, Ludwig Maximilian University of Munich21, Greifswald University Hospital22, Butler Hospital23, Shaare Zedek Medical Center24, Rutgers University25, Stellenbosch University26, Baylor College of Medicine27, University College London28, Memorial Hospital of South Bend29, University of Bonn30, University of California, San Francisco31, University of California, Irvine32, University of Utah33, National Institutes of Health34, University of California, Los Angeles35, St George's Hospital36, Federal University of São Paulo37, Wayne State University38, McGill University39, University of Cologne40, Federal University of Bahia41, VU University Amsterdam42, University of Cape Town43, Utrecht University44, Vanderbilt University45, Netherlands Institute for Neuroscience46, Erasmus University Rotterdam47, University of Michigan48, German Center for Neurodegenerative Diseases49, University of British Columbia50
TL;DR: The results indicate that there is some genetic overlap between these two phenotypically-related neuropsychiatric disorders, but suggest that the two disorders have distinct genetic architectures.
Abstract: The direct estimation of heritability from genome-wide common variant data as implemented in the program Genome-wide Complex Trait Analysis (GCTA) has provided a means to quantify heritability attributable to all interrogated variants. We have quantified the variance in liability to disease explained by all SNPs for two phenotypically-related neurobehavioral disorders, obsessive-compulsive disorder (OCD) and Tourette Syndrome (TS), using GCTA. Our analysis yielded a heritability point estimate of 0.58 (se = 0.09, p = 5.64e-12) for TS, and 0.37 (se = 0.07, p = 1.5e-07) for OCD. In addition, we conducted multiple genomic partitioning analyses to identify genomic elements that concentrate this heritability. We examined genomic architectures of TS and OCD by chromosome, MAF bin, and functional annotations. In addition, we assessed heritability for early onset and adult onset OCD. Among other notable results, we found that SNPs with a minor allele frequency of less than 5% accounted for 21% of the TS heritability and 0% of the OCD heritability. Additionally, we identified a significant contribution to TS and OCD heritability by variants significantly associated with gene expression in two regions of the brain (parietal cortex and cerebellum) for which we had available expression quantitative trait loci (eQTLs). Finally we analyzed the genetic correlation between TS and OCD, revealing a genetic correlation of 0.41 (se = 0.15, p = 0.002). These results are very close to previous heritability estimates for TS and OCD based on twin and family studies, suggesting that very little, if any, heritability is truly missing (i.e., unassayed) from TS and OCD GWAS studies of common variation. The results also indicate that there is some genetic overlap between these two phenotypically-related neuropsychiatric disorders, but suggest that the two disorders have distinct genetic architectures.
307 citations
TL;DR: The biological and clinical relevance of TARDBP and FUS mutations in ALS is summarized and functional characterization of these mutations in in vitro and in vivo systems is helping to better understand how motor neuron degeneration occurs.
Abstract: Mutations in the TAR DNA Binding Protein gene (TARDBP), encoding the protein TDP-43, were identified in amyotrophic lateral sclerosis (ALS) patients. Interestingly, TDP-43 positive inclusion bodies were first discovered in ubiquitin-positive, tau-negative ALS and frontotemporal dementia (FTD) inclusion bodies, and subsequently observed in the majority of neurodegenerative disorders. To date, 47 missense and one truncating mutations have been described in a large number of familial (FALS) and sporadic (SALS) patients. Fused in sarcoma (FUS) was found to be responsible for a previously identified ALS6 locus, being mutated in both FALS and SALS patients. TARDBP and FUS have a structural and functional similarity and most of mutations in both genes are also clustered in the C-terminus of the proteins. The molecular mechanisms through which mutant TDP-43 and FUS may cause motor neuron degeneration are not well understood. Both proteins play an important role in mRNA transport, axonal maintenance, and motor neuron development. Functional characterization of these mutations in in vitro and in vivo systems is helping to better understand how motor neuron degeneration occurs. This report summarizes the biological and clinical relevance of TARDBP and FUS mutations in ALS. All the data reviewed here have been submitted to a database based on the Leiden Open (source) Variation Database (LOVD) and is accessible online at www.lovd.nl/TARDBP, www.lovd.nl/FUS.
230 citations
Stanford University1, University of Copenhagen2, University of Groningen3, French Institute of Health and Medical Research4, Pierre-and-Marie-Curie University5, University of Marburg6, University of Regensburg7, University of Bologna8, Leiden University Medical Center9, Charles University in Prague10, Université de Montréal11, Innsbruck Medical University12, University of Strasbourg13, Hospital General Universitario Gregorio Marañón14, University of Virginia15, Cincinnati Children's Hospital Medical Center16, Versailles Saint-Quentin-en-Yvelines University17, Paris Descartes University18, Wellcome Trust Sanger Institute19
TL;DR: For example, the authors found that three loci located outside the Human Leukocyte Antigen (HLA) region on chromosome 6 were significantly associated with disease risk, including Cathepsin H (CTSH), Tumor necrosis factor (ligand) superfamily member 4 (TNFSF4), and OX40L.
Abstract: Recent advances in the identification of susceptibility genes and environmental exposures provide broad support for a post-infectious autoimmune basis for narcolepsy/hypocretin (orexin) deficiency. We genotyped loci associated with other autoimmune and inflammatory diseases in 1,886 individuals with hypocretin-deficient narcolepsy and 10,421 controls, all of European ancestry, using a custom genotyping array (ImmunoChip). Three loci located outside the Human Leukocyte Antigen (HLA) region on chromosome 6 were significantly associated with disease risk. In addition to a strong signal in the T cell receptor alpha (TRA@), variants in two additional narcolepsy loci, Cathepsin H (CTSH) and Tumor necrosis factor (ligand) superfamily member 4 (TNFSF4, also called OX40L), attained genome-wide significance. These findings underline the importance of antigen presentation by HLA Class II to T cells in the pathophysiology of this autoimmune disease.
213 citations
TL;DR: It is suggested that accurate phenotype delineation may be more important for detecting true genetic associations than increase in sample size, as well as the impact of heterogeneity on the statistical power of genome wide association studies (GWAS).
Abstract: Phenotypic misclassification (between cases) has been shown to reduce the power to detect association in genetic studies. However, it is conceivable that complex traits are heterogeneous with respect to individual genetic susceptibility and disease pathophysiology, and that the effect of heterogeneity has a larger magnitude than the effect of phenotyping errors. Although an intuitively clear concept, the effect of heterogeneity on genetic studies of common diseases has received little attention. Here we investigate the impact of phenotypic and genetic heterogeneity on the statistical power of genome wide association studies (GWAS). We first performed a study of simulated genotypic and phenotypic data. Next, we analyzed the Wellcome Trust Case-Control Consortium (WTCCC) data for diabetes mellitus (DM) type 1 (T1D) and type 2 (T2D), using varying proportions of each type of diabetes in order to examine the impact of heterogeneity on the strength and statistical significance of association previously found in the WTCCC data. In both simulated and real data, heterogeneity (presence of “non-cases”) reduced the statistical power to detect genetic association and greatly decreased the estimates of risk attributed to genetic variation. This finding was also supported by the analysis of loci validated in subsequent large-scale meta-analyses. For example, heterogeneity of 50% increases the required sample size by approximately three times. These results suggest that accurate phenotype delineation may be more important for detecting true genetic associations than increase in sample size.
189 citations
TL;DR: This study confirms the involvement of SYNGAP1 in autism while providing novel insight into the epileptic manifestations associated with its disruption, and suggests that the de novo missense mutations, p.R579X, and possibly all the other truncating mutations in SYngAP1 result in a loss of its function.
Abstract: De novo mutations in SYNGAP1, which codes for a RAS/RAP GTP-activating protein, cause nonsyndromic intellectual disability (NSID). All disease-causing point mutations identified until now in SYNGAP1 are truncating, raising the possibility of an association between this type of mutations and NSID. Here, we report the identification of the first pathogenic missense mutations (c.1084T>C [p.W362R], c.1685C>T [p.P562L]) and three novel truncating mutations (c.283dupC [p.H95PfsX5], c.2212_2213del [p.S738X], and (c.2184del [p.N729TfsX31]) in SYNGAP1 in patients with NSID. A subset of these patients also showed ataxia, autism, and a specific form of generalized epilepsy that can be refractory to treatment. All of these mutations occurred de novo, except c.283dupC, which was inherited from a father who is a mosaic. Biolistic transfection of wild-type SYNGAP1 in pyramidal cells from cortical organotypic cultures significantly reduced activity-dependent phosphorylated extracellular signal-regulated kinase (pERK) levels. In contrast, constructs expressing p.W362R, p.P562L, or the previously described p.R579X had no significant effect on pERK levels. These experiments suggest that the de novo missense mutations, p.R579X, and possibly all the other truncating mutations in SYNGAP1 result in a loss of its function. Moreover, our study confirms the involvement of SYNGAP1 in autism while providing novel insight into the epileptic manifestations associated with its disruption.
189 citations
TL;DR: A genetic model of ALS is generated to explore the biological consequences of a null mutation of the Caenorhabditis elegans C9ORF72 orthologue, F18A1.6, and it is observed that the motor defects caused by loss of alfa-1 were additive with the toxicity caused by mutant TDP-43 proteins, but not by the mutant FUS proteins.
Abstract: An expansion of the hexanucleotide GGGGCC repeat in the first intron of C9ORF72 gene was recently linked to amyotrophic lateral sclerosis It is not known if the mutation results in a gain of function, a loss of function or if, perhaps both mechanisms are linked to pathogenesis We generated a genetic model of ALS to explore the biological consequences of a null mutation of the Caenorhabditis elegans C9ORF72 orthologue, F18A16, also called alfa-1 alfa-1 mutants displayed age-dependent motility defects leading to paralysis and the specific degeneration of GABAergic motor neurons alfa-1 mutants showed differential susceptibility to environmental stress where osmotic stress provoked neurodegeneration Finally, we observed that the motor defects caused by loss of alfa-1 were additive with the toxicity caused by mutant TDP-43 proteins, but not by the mutant FUS proteins These data suggest that a loss of alfa-1/C9ORF72 expression may contribute to motor neuron degeneration in a pathway associated with other known ALS genes
174 citations
Broad Institute1, Harvard University2, University of California, San Francisco3, University of British Columbia4, University of Chicago5, University of Southern California6, University of California, Los Angeles7, Université de Montréal8, Utrecht University9, VU University Amsterdam10, Yale University11, University of Toronto12, Shaare Zedek Medical Center13, North Shore-LIJ Health System14, Hofstra University15, New York University16, Cleveland Clinic17, Medical City Dallas Hospital18, University College London19, Wellcome Trust Sanger Institute20, University of Antioquia21, University of Hong Kong22, Pontifical Bolivarian University23, Cold Spring Harbor Laboratory24, University of Utah25, Johns Hopkins University26, Cornell University27, Baylor College of Medicine28, Rutgers University29, University of Cincinnati30, University of Groningen31, St George's, University of London32, Memorial Hospital of South Bend33, University of Illinois at Chicago34, National Institutes of Health35, University of Bonn36, Erasmus University Rotterdam37, Stanford University38, Icahn School of Medicine at Mount Sinai39
TL;DR: This study lays the groundwork for the eventual identification of common TS susceptibility variants in larger cohorts and helps to provide a more complete understanding of the full genetic architecture of this disorder.
Abstract: Tourette's syndrome (TS) is a developmental disorder that has one of the highest familial recurrence rates among neuropsychiatric diseases with complex inheritance. However, the identification of definitive TS susceptibility genes remains elusive. Here, we report the first genome-wide association study (GWAS) of TS in 1285 cases and 4964 ancestry-matched controls of European ancestry, including two European-derived population isolates, Ashkenazi Jews from North America and Israel and French Canadians from Quebec, Canada. In a primary meta-analysis of GWAS data from these European ancestry samples, no markers achieved a genome-wide threshold of significance (P<5 × 10−8); the top signal was found in rs7868992 on chromosome 9q32 within COL27A1 (P=1.85 × 10−6). A secondary analysis including an additional 211 cases and 285 controls from two closely related Latin American population isolates from the Central Valley of Costa Rica and Antioquia, Colombia also identified rs7868992 as the top signal (P=3.6 × 10−7 for the combined sample of 1496 cases and 5249 controls following imputation with 1000 Genomes data). This study lays the groundwork for the eventual identification of common TS susceptibility variants in larger cohorts and helps to provide a more complete understanding of the full genetic architecture of this disorder.
154 citations
TL;DR: This study shows that, although rare, C9orf72 repeat expansions may be associated with clinically typical Parkinson's disease and also with other parkinsonism, and provides the tools for identifying parkinsonian patients with C 9orf72 expansions, with important consequences for genetic counselling.
Abstract: The recently identified C9orf72 gene accounts for a large proportion of amyotrophic lateral sclerosis and frontotemporal lobar degenerations. As several forms of these disorders are associated with parkinsonism, we hypothesized that some patients with Parkinson's disease or other forms of parkinsonism might carry pathogenic C9orf72 expansions. Therefore, we looked for C9orf72 repeat expansions in 1446 unrelated parkinsonian patients consisting of 1225 patients clinically diagnosed with Parkinson's disease, 123 with progressive supranuclear palsy, 21 with corticobasal degeneration syndrome, 43 with Lewy body dementia and 25 with multiple system atrophy-parkinsonism. Of the 1446 parkinsonian patients, five carried C9orf72 expansions: three patients with typical Parkinson's disease, one with corticobasal degeneration syndrome and another with progressive supranuclear palsy. This study shows that (i) although rare, C9orf72 repeat expansions may be associated with clinically typical Parkinson's disease and also with other parkinsonism; (ii) in several patients, parkinsonism was levodopa-responsive and remained pure, without associated dementia, for >10 years and (iii) interestingly, all C9orf72 repeat expansion carriers had positive family histories of parkinsonism, degenerative dementias or amyotrophic lateral sclerosis. This study also provides the tools for identifying parkinsonian patients with C9orf72 expansions, with important consequences for genetic counselling.
148 citations
TL;DR: Interestingly, although the catabolism of gangliosides is implicated in a variety of neurological diseases, SPG26 is only the second human disease involving defects of their biosynthesis, and these findings confirm the increasing interest of lipid metabolism in HSPs.
Abstract: Hereditary spastic paraplegias (HSPs) form a heterogeneous group of neurological disorders. A whole-genome linkage mapping effort was made with three HSP-affected families from Spain, Portugal, and Tunisia and it allowed us to reduce the SPG26 locus interval from 34 to 9 Mb. Subsequently, a targeted capture was made to sequence the entire exome of affected individuals from these three families, as well as from two additional autosomal-recessive HSP-affected families of German and Brazilian origins. Five homozygous truncating (n = 3) and missense (n = 2) mutations were identified in B4GALNT1. After this finding, we analyzed the entire coding region of this gene in 65 additional cases, and three mutations were identified in two subjects. All mutated cases presented an early-onset spastic paraplegia, with frequent intellectual disability, cerebellar ataxia, and peripheral neuropathy as well as cortical atrophy and white matter hyperintensities on brain imaging. B4GALNT1 encodes β-1,4-N-acetyl-galactosaminyl transferase 1 (B4GALNT1), involved in ganglioside biosynthesis. These findings confirm the increasing interest of lipid metabolism in HSPs. Interestingly, although the catabolism of gangliosides is implicated in a variety of neurological diseases, SPG26 is only the second human disease involving defects of their biosynthesis.
Duke University1, Tel Aviv University2, Sheba Medical Center3, University of Toronto4, Weizmann Institute of Science5, Wolfson Medical Center6, Necker-Enfants Malades Hospital7, Université de Montréal8, Children's Hospital of Philadelphia9, University of Dhaka10, Montreal Neurological Institute and Hospital11
TL;DR: It is shown that recessive mutations in the ASNS gene are responsible for this syndrome and that asparagine synthesis is essential for the development and function of the brain but not for that of other organs.
University of Tokyo1, National Institute of Genetics2, University of Turku3, Ehime University4, Centre Hospitalier Universitaire Sainte-Justine5, Université de Montréal6, Osaka Medical College7, Niigata University8, Aichi Medical University9, Nagoya University10, Macquarie University11, University of Sydney12, University of Massachusetts Medical School13, Turku University Hospital14, McGill University15, Montreal Neurological Institute and Hospital16
TL;DR: It is indicated that disruption of the neuregulin-ErbBB4 pathway is involved in the pathogenesis of ALS and potentially paves the way for the development of innovative therapeutic strategies such using NRGs or their agonists to upregulate ErbB4 functions.
Abstract: Amyotrophic lateral sclerosis (ALS) is a devastating neurological disorder characterized by the degeneration of motor neurons and typically results in death within 3–5 years from onset. Familial ALS (FALS) comprises 5%–10% of ALS cases, and the identification of genes associated with FALS is indispensable to elucidating the molecular pathogenesis. We identified a Japanese family affected by late-onset, autosomal-dominant ALS in which mutations in genes known to be associated with FALS were excluded. A whole- genome sequencing and parametric linkage analysis under the assumption of an autosomal-dominant mode of inheritance with incomplete penetrance revealed the mutation c.2780G>A (p. Arg927Gln) in ERBB4. An extensive mutational analysis revealed the same mutation in a Canadian individual with familial ALS and a de novo mutation, c.3823C>T (p. Arg1275Trp), in a Japanese simplex case. These amino acid substitutions involve amino acids highly conserved among species, are predicted as probably damaging, and are located within a tyrosine kinase domain (p. Arg927Gln) or a C-terminal domain (p. Arg1275Trp), both of which mediate essential functions of ErbB4 as a receptor tyrosine kinase. Functional analysis revealed that these mutations led to a reduced autophosphorylation of ErbB4 upon neuregulin-1 (NRG-1) stimulation. Clinical presentations of the individuals with mutations were characterized by the involvement of both upper and lower motor neurons, a lack of obvious cognitive dysfunction, and relatively slow progression. This study indicates that disruption of the neuregulin-ErbB4 pathway is involved in the pathogenesis of ALS and potentially paves the way for the development of innovative therapeutic strategies such using NRGs or their agonists to upregulate ErbB4 functions.
TL;DR: It is suggested that both recessive and dominant mutations in RARB cause anophthalmia and/or microphthalmia and diaphragmatic hernia, providing further evidence of the crucial role of the retinoic acid pathway during eye development and organogenesis.
Abstract: Anophthalmia and/or microphthalmia, pulmonary hypoplasia, diaphragmatic hernia, and cardiac defects are the main features of PDAC syndrome. Recessive mutations in STRA6, encoding a membrane receptor for the retinol-binding protein, have been identified in some cases with PDAC syndrome, although many cases have remained unexplained. Using whole-exome sequencing, we found that two PDAC-syndrome-affected siblings, but not their unaffected sibling, were compound heterozygous for nonsense (c.355C>T [p.Arg119∗]) and frameshift (c.1201_1202insCT [p.Ile403Serfs∗15]) mutations in retinoic acid receptor beta (RARB). Transfection studies showed that p.Arg119∗ and p.Ile403Serfs∗15 altered RARB had no transcriptional activity in response to ligands, confirming that the mutations induced a loss of function. We then sequenced RARB in 15 subjects with anophthalmia and/or microphthalmia and at least one other feature of PDAC syndrome. Surprisingly, three unrelated subjects with microphthalmia and diaphragmatic hernia showed de novo missense mutations affecting the same codon; two of the subjects had the c.1159C>T (Arg387Cys) mutation, whereas the other one carried the c.1159C>A (p.Arg387Ser) mutation. We found that compared to the wild-type receptor, p.Arg387Ser and p.Arg387Cys altered RARB induced a 2- to 3-fold increase in transcriptional activity in response to retinoic acid ligands, suggesting a gain-of-function mechanism. Our study thus suggests that both recessive and dominant mutations in RARB cause anophthalmia and/or microphthalmia and diaphragmatic hernia, providing further evidence of the crucial role of the retinoic acid pathway during eye development and organogenesis.
TL;DR: Mitochondrial damage, including increased mitochondrial volume, excess superoxide production and increased exposure of the toxic BH3 domain of Bcl-2, tracks positively with the presence of misfolded SOD1.
Abstract: Mutant superoxide dismutase 1 (SOD1) selectively associates with spinal cord mitochondria in rodent models of SOD1-mediated amyotrophic lateral sclerosis. A portion of mutant SOD1 exists in a non-native/misfolded conformation that is selectively recognized by conformational antibodies. Misfolded SOD1 is common to all mutant SOD1 models, is uniquely found in areas affected by the disease and is considered to mediate toxicity. We report that misfolded SOD1 recognized by the antibody B8H10 is present in greater abundance in mitochondrial fractions of SOD1(G93A) rat spinal cords compared with oxidized SOD1, as recognized by the C4F6 antibody. Using a novel flow cytometric assay, we detect an age-dependent deposition of B8H10-reactive SOD1 on spinal cord mitochondria from both SOD1(G93A) rats and SOD1(G37R) mice. Mitochondrial damage, including increased mitochondrial volume, excess superoxide production and increased exposure of the toxic BH3 domain of Bcl-2, tracks positively with the presence of misfolded SOD1. Lastly, B8H10 reactive misfolded SOD1 is present in the lysates and mitochondrial fractions of lymphoblasts derived from ALS patients carrying SOD1 mutations, but not in controls. Together, these results highlight misfolded SOD1 as common to two ALS rodent animal models and familial ALS patient lymphoblasts with four different SOD1 mutations. Studies in the animal models point to a role for misfolded SOD1 in mitochondrial dysfunction in ALS pathogenesis.
TL;DR: The whole-exome sequences of French-Canadian individuals are analyzed to highlight the impact of population demography on genetic fitness and the contribution of rare variants to the human genetic variation landscape, emphasizing the need for deep cataloguing of genetic variants by resequencing worldwide human populations in order to truly assess disease risk.
Abstract: Whole-exome or gene targeted resequencing in hundreds to thousands of individuals has shown that the majority of genetic variants are at low frequency in human populations. Rare variants are enriched for functional mutations and are expected to explain an important fraction of the genetic etiology of human disease, therefore having a potential medical interest. In this work, we analyze the whole-exome sequences of French-Canadian individuals, a founder population with a unique demographic history that includes an original population bottleneck less than 20 generations ago, followed by a demographic explosion, and the whole exomes of French individuals sampled from France. We show that in less than 20 generations of genetic isolation from the French population, the genetic pool of French-Canadians shows reduced levels of diversity, higher homozygosity, and an excess of rare variants with low variant sharing with Europeans. Furthermore, the French-Canadian population contains a larger proportion of putatively damaging functional variants, which could partially explain the increased incidence of genetic disease in the province. Our results highlight the impact of population demography on genetic fitness and the contribution of rare variants to the human genetic variation landscape, emphasizing the need for deep cataloguing of genetic variants by resequencing worldwide human populations in order to truly assess disease risk.
TL;DR: Overexpression of VAPB mutations were unable to rescue the motor deficit caused by Vapb knockdown in zebrafish and failed to cause a toxic gain-of-function defect on their own, indicating that VapB loss of function weakens the motor system of vertebrate animal models but is on its own unable to lead to a complete ALS phenotype.
Abstract: The mutations P56S and T46I in the gene encoding vesicle-associated membrane protein-associated protein B/C (VAPB) cause ALS8, a familial form of amyotrophic lateral sclerosis (ALS). Overexpression of mutant forms of VAPB leads to cytosolic aggregates, suggesting a gain of function of the mutant protein. However, recent work suggested that the loss of VAPB function could be the major mechanism leading to ALS8. Here, we used multiple genetic and experimental approaches to study whether VAPB loss of function might be sufficient to trigger motor neuron degeneration. In order to identify additional ALS-associated VAPB mutations, we screened the entire VAPB gene in a cohort of ALS patients and detected two mutations (A145V and S160Δ). To directly address the contribution of VAPB loss of function in ALS, we generated zebrafish and mouse models with either a decreased or a complete loss of Vapb expression. Vapb knockdown in zebrafish led to swimming deficits. Mice knocked-out for Vapb showed mild motor deficits after 18 months of age yet had innervated neuromuscular junctions (NMJs). Importantly, overexpression of VAPB mutations were unable to rescue the motor deficit caused by Vapb knockdown in zebrafish and failed to cause a toxic gain-of-function defect on their own. Thus, Vapb loss of function weakens the motor system of vertebrate animal models but is on its own unable to lead to a complete ALS phenotype. Our findings are consistent with the notion that VAPB mutations constitute a risk factor for motor neuron disease through a loss of VAPB function.
TL;DR: Pain in patients with mTBI was associated with more rapid qEEG activity, mostly during REM sleep, suggesting that pain is associated with poor sleep and is a critical factor in managing post-concussion symptoms.
Abstract: Chronic pain is a highly prevalent post-concussion symptom occurring in a majority of patients with mild traumatic brain injury (mTBI). About half of patients with mTBI report sleep–wake disturbances. It is known that pain can alter sleep quality in this population, but the interaction between pain and sleep is not fully understood. This study aimed to identify how pain affects subjective sleep (Pittsburgh Sleep Quality Index [PSQI]), sleep architecture, and quantitative electroencephalographic (qEEG) brain activity after mTBI. Twenty-four mTBI patients complaining of sleep–wake disturbances, with and without pain (8 and 16, respectively), were recruited 45 (±22.7) days post-trauma on average. Data were compared with those of 18 healthy controls (no sleep or pain complaints). The PSQI, sleep architecture, and qEEG activity were analyzed. Pain was assessed using questionnaires and a 100-mm visual analogue scale. Patients with mTBI reported three times poorer sleep quality than controls on the PSQI...
TL;DR: The finding that the p.R263Q mutation impaired DDX11 helicase activity by perturbing its DNA binding and DNA‐dependent ATP hydrolysis is confirmed and provides novel insight into the structural requirement forDDX11 activity.
Abstract: Mutations in the gene encoding the iron-sulfur-containing DNA helicase DDX11 (ChlR1) were recently identified as a cause of a new recessive cohesinopathy, Warsaw breakage syndrome (WABS), in a single patient with severe microcephaly, pre- and postnatal growth retardation, and abnormal skin pigmentation. Here, using homozygosity mapping in a Lebanese consanguineous family followed by exome sequencing, we identified a novel homozygous mutation (c.788G>A [p.R263Q]) in DDX11 in three affected siblings with severe intellectual disability and many of the congenital abnormalities reported in the WABS original case. Cultured lymphocytes from the patients showed increased mitomycin C-induced chromosomal breakage, as found in WABS. Biochemical studies of purified recombinant DDX11 indicated that the p.R263Q mutation impaired DDX11 helicase activity by perturbing its DNA binding and DNA-dependent ATP hydrolysis. Our findings thus confirm the involvement of DDX11 in WABS, describe its phenotypical spectrum, and provide novel insight into the structural requirement for DDX11 activity.
TL;DR: It is found that histone modification marks were significantly increased in bipolar disorder and major depression and this effect was correlated with significant increases in gene expression, suggesting that synapsin dysregulation in mood disorders is mediated in part by epigenetic regulatory mechanisms.
Abstract: The synapsin family of neuronal phosphoproteins is composed of three genes (SYN1, SYN2 and SYN3) with alternative splicing resulting in a number of variants with various levels of homology. These genes have been postulated to play significant roles in several neuropsychiatric disorders, including bipolar disorder, schizophrenia and epilepsy. Epigenetic regulatory mechanisms, such as histone modifications in gene regulatory regions, have also been proposed to play a role in a number of psychiatric disorders, including bipolar disorder and major depressive disorder. One of the best characterized histone modifications is histone 3 lysine 4 tri-methylation (H3K4me3), an epigenetic mark shown to be highly enriched at transcriptional start sites and associated with active transcription. In the present study we have quantified the expression of transcript variants of the three synapsin genes and investigated their relationship to H3K4me3 promoter enrichment in post-mortem brain samples. We found that histone modification marks were significantly increased in bipolar disorder and major depression and this effect was correlated with significant increases in gene expression. Our findings suggest that synapsin dysregulation in mood disorders is mediated in part by epigenetic regulatory mechanisms.
TL;DR: DNAJC5, which encodes the cysteine string protein (CSPα), a presynaptic protein implicated in neurodegeneration, causes autosomal dominant Kufs disease, and the leucine residues at positions 115 and 116 are hotspots for mutations and result in a homogeneous phenotype of progressive myoclonus epilepsy with onset around 30 years old.
Abstract: We sought to identify the molecular basis of the autosomal dominant form of Kufs disease, an adult onset form of neuronal ceroid lipofuscinosis. We used a combination of classic linkage analysis and Next Generation Sequencing to map and identify mutations in DNAJC5 in a total of three families. We analyzed the clinical manifestations in 20 individuals with mutation in DNAJC5. We report here the mapping and the identification of a p.L116del mutation in DNAJC5 segregating with the disease in two distinct American families, as well as a p.L115R mutation in an additional family. The age of onset and clinical manifestations were very homogeneous among mutation positive individuals, including generalized tonic-clonic seizures, myoclonus, ataxia, speech deterioration, dementia, and premature death. A few individuals also exhibited parkinsonism. DNAJC5, which encodes the cysteine string protein (CSPα), a presynaptic protein implicated in neurodegeneration, causes autosomal dominant Kufs disease. The leucine residues at positions 115 and 116 are hotspots for mutations and result in a homogeneous phenotype of progressive myoclonus epilepsy with onset around 30 years old.
TL;DR: This is the first report of ASD patients with truncating mutations in GABA receptors genes, and missense and silent variants in nuclear RNA export factor 5 and histone deacetylase 6 were shown to partially disrupt the protein.
Abstract: A large-scale sequencing screen of X-linked synaptic genes in individuals with autism spectrum disorder (ASD) or schizophrenia (SCZ), two common neurodevelopmental disorders, identified many variants most of which have no easily predictable effect on gene function. In this report, we evaluated the impact of these rare missense and silent variants on gene splicing. For this purpose, we used complementary in silico analyses, in vitro minigene-based assays and RNA prepared from lymphoblastoid cells derived from patients with these mutations. Our goal was to identify the variants which might either create or disrupt an acceptor splice site, a donor splice site or an exonic splicing enhancer, thus leading to aberrant splicing that could be involved in the pathogenesis of ASD or SCZ. We identified truncating mutations in distinct X-linked gamma-aminobutyric acid A (GABAA) receptor subunit-encoding genes, GABRQ and GABRA3, in two different families. Furthermore, missense and silent variants in nuclear RNA export factor 5 and histone deacetylase 6 were shown to partially disrupt the protein. While genes from the GABAergic pathway have previously been thought to be involved in the pathophysiology of ASD, this is the first report of ASD patients with truncating mutations in GABA receptors genes.
TL;DR: The second report, to the authors' knowledge, of SYNE1 gene mutations in a population other than FCs is reported, suggesting that mutations in SYne1 should be investigated in families with cerebellar ataxia who live outside the FC region.
Abstract: Importance Autosomal recessive cerebellar ataxia type I, also known as recessive ataxia of Beauce, is a slowly progressive ataxia that leads to moderate disability with gait ataxia, dysarthria, dysmetria, mild oculomotor abnormalities, and diffuse cerebellar atrophy on brain imaging. Mutations in the synaptic nuclear envelope protein 1 ( SYNE1 ) gene, located on chromosome 6p25, were first reported in patients who originated from a region known as “Beauce” in the province of Quebec, Canada. Objective To better evaluate the prevalence of SYNE1 mutations in individuals with mild pure cerebellar ataxia and cerebellar atrophy, we screened the gene in additional French-Canadian (FC) families and individuals from other populations. Design, Setting, and Participants Study participants were referred by their treating physician on the basis of core features of autosomal recessive cerebellar ataxia type I. After excluding individuals with known SYNE1 mutations, our cohort was composed mainly of 19 FCs and 21 individuals from other ethnic backgrounds. Interventions Extraction of DNA from blood samples and complete resequencing of the SYNE1 gene. Main Outcomes and Measures The involvement of SYNE1 mutations in individuals with ataxia worldwide by resequencing the SYNE1 gene. Results Two novel truncating mutations were found among the FC participants, and 2 other novel mutations were found in a patient from France and a patient from Brazil (1 mutation each). Conclusions and Relevance This is the second report, to our knowledge, of SYNE1 gene mutations in a population other than FCs. These data suggest that mutations in SYNE1 should be investigated in families with cerebellar ataxia who live outside the FC region.
TL;DR: In this paper, a pharmacological manipulation of a Wnt signaling pathway using lithium chloride (LiCl), a GSK-3β inhibitor, and observed the enhanced expression of β-catenin protein as well as the decreased cell death normally observed in an Oculopharyngeal muscular dystrophy (OPMD) cell model of murine myoblast (C2C12) expressing the expanded and pathogenic form of the expPABPN1.
Abstract: Expansion of polyalanine tracts causes at least nine inherited human diseases. Among these, a polyalanine tract expansion in the poly (A)-binding protein nuclear 1 (expPABPN1) causes oculopharyngeal muscular dystrophy (OPMD). So far, there is no treatment for OPMD patients. Developing drugs that efficiently sustain muscle protection by activating key cell survival mechanisms is a major challenge in OPMD research. Proteins that belong to the Wnt family are known for their role in both human development and adult tissue homeostasis. A hallmark of the Wnt signaling pathway is the increased expression of its central effector, beta-catenin (β-catenin) by inhibiting one of its upstream effector, glycogen synthase kinase (GSK)3β. Here, we explored a pharmacological manipulation of a Wnt signaling pathway using lithium chloride (LiCl), a GSK-3β inhibitor, and observed the enhanced expression of β-catenin protein as well as the decreased cell death normally observed in an OPMD cell model of murine myoblast (C2C12) expressing the expanded and pathogenic form of the expPABPN1. Furthermore, this effect was also observed in primary cultures of mouse myoblasts expressing expPABPN1. A similar effect on β-catenin was also observed when lymphoblastoid cells lines (LCLs) derived from OPMD patients were treated with LiCl. We believe manipulation of the Wnt/β-catenin signaling pathway may represent an effective route for the development of future therapy for patients with OPMD.
TL;DR: The study suggests that disruption of TBC1D7 causes ID but without the other typical features found in TSC, which reinforces the relationship between this pathway and the development of megalencephaly.
Abstract: Background Mutations in TSC1 or TSC2 cause the tuberous sclerosis complex (TSC), a disorder characterised by the development of hamartomas or benign tumours in various organs as well as the variable presence of epilepsy, intellectual disability (ID) and autism. TSC1, TSC2 and the recently described protein TBC1D7 form a complex that inhibits mTORC1 signalling and limits cell growth. Although it has been proposed that mutations in TBC1D7 might also cause TSC, loss of its function has not yet been documented in humans.
Methods and Results We used homozygosity mapping and exome sequencing to study a consanguineous family with ID and megalencephaly but without any specific features of TSC. We identified only one rare coding variant, c.538delT:p.Y180fsX1 in TBC1D7 , in the regions of homozygosity shared by the affected siblings. We show that this mutation abolishes TBC1D7 expression and is associated with increased mTORC1 signalling in cells of the affected individuals.
Conclusions Our study suggests that disruption of TBC1D7 causes ID but without the other typical features found in TSC. Although megalencephaly is not commonly observed in TSC, it has been associated with mTORC1 activation. Our observation thus reinforces the relationship between this pathway and the development of megalencephaly.
University of Turin1, University of Pittsburgh2, University of Bologna3, Universidade Federal do Rio Grande do Sul4, Alfred I. duPont Hospital for Children5, University of São Paulo6, French Institute of Health and Medical Research7, Uppsala University8, Tel Aviv University9, Sheba Medical Center10, Heidelberg University11, University of California, Los Angeles12, Montreal Neurological Institute and Hospital13, Children's National Medical Center14, Boston Children's Hospital15, Thomas Jefferson University16, University of Delaware17
TL;DR: The detailed molecular analysis of the largest collection of ADLD families studied, to date, has identified the minimal duplicated region necessary for the disease, defined all the duplication junctions at the nucleotide level and identified the first inverted LMNB1 duplication.
Abstract: Autosomal dominant leukodystrophy (ADLD) is an adult onset demyelinating disorder that is caused by duplications of the lamin B1 (LMNB1) gene. However, as only a few cases have been analyzed in detail, the mechanisms underlying LMNB1 duplications are unclear. We report the detailed molecular analysis of the largest collection of ADLD families studied, to date. We have identified the minimal duplicated region necessary for the disease, defined all the duplication junctions at the nucleotide level and identified the first inverted LMNB1 duplication. We have demonstrated that the duplications are not recurrent; patients with identical duplications share the same haplotype, likely inherited from a common founder and that the duplications originated from intrachromosomal events. The duplication junction sequences indicated that nonhomologous end joining or replication-based mechanisms such fork stalling and template switching or microhomology-mediated break induced repair are likely to be involved. LMNB1 expression was increased in patients' fibroblasts both at mRNA and protein levels and the three LMNB1 alleles in ADLD patients show equal expression, suggesting that regulatory regions are maintained within the rearranged segment. These results have allowed us to elucidate duplication mechanisms and provide insights into allele-specific LMNB1 expression levels.
TL;DR: No mutations were identified in this cohort suggesting that PFN1 gene mutations are a very rare cause of familial ALS among patients with predominantly European ancestry.
TL;DR: It is reported that misfolded SOD1 recognized by the antibody B8H10 is present in greater abundance in mitochondrial fractions of Sod1 rat spinal cords compared with oxidized S OD1, as recognized byThe C4F6 antibody.
Abstract: Mutant superoxide dismutase 1 (SOD1) selectively associates with spinal cord mitochondria in rodent models of SOD1-mediated amyotrophic lateral sclerosis. A portion of mutant SOD1 exists in a non-native/misfolded conformation that is selectively recognized by conformational antibodies. Misfolded SOD1 is common to all mutant SOD1 models, is uniquely found in areas affected by the disease and is considered to mediate toxicity. We report that misfolded SOD1 recognized by the antibody B8H10 is present in greater abundance in mitochondrial fractions of SOD1(G93A) rat spinal cords compared with oxidized SOD1, as recognized by the C4F6 antibody. Using a novel flow cytometric assay, we detect an age-dependent deposition of B8H10-reactive SOD1 on spinal cord mitochondria from both SOD1(G93A) rats and SOD1(G37R) mice. Mitochondrial damage, including increased mitochondrial volume, excess superoxide production and increased exposure of the toxic BH3 domain of Bcl-2, tracks positively with the presence of misfolded SOD1. Lastly, B8H10 reactive misfolded SOD1 is present in the lysates and mitochondrial fractions of lymphoblasts derived from ALS patients carrying SOD1 mutations, but not in controls. Together, these results highlight misfolded SOD1 as common to two ALS rodent animal models and familial ALS patient lymphoblasts with four different SOD1 mutations. Studies in the animal models point to a role for misfolded SOD1 in mitochondrial dysfunction in ALS pathogenesis.
TL;DR: Although essential tremor has a genetic basis, specific genes have not been identified, and a non‐sense mutation in the amyotrophic lateral sclerosis gene fused in sarcoma/translated in liposarcoma (FUS/TLS) was identified by exome sequencing.
Abstract: Background and purpose
Although essential tremor (ET) has a genetic basis, specific genes have not been identified. Recently, in a large ET family (FET1) from Quebec, a non-sense mutation (p.Q290X) in the amyotrophic lateral sclerosis (ALS) gene fused in sarcoma/translated in liposarcoma (FUS/TLS) was identified by exome sequencing. No confirmatory studies have been published.
Methods
Two-hundred and fifty-nine ET cases and 262 controls were enrolled in a study at Columbia University. We performed a comprehensive analysis of the FUS/TLS gene by sequencing all exons in a subsample of 116 ET cases with early-onset (≤40 years) ET. We evaluated an association between ET and SNPs in the FUS/TLS gene by genotyping four haplotype tagging SNPs in all 259 ET cases and 262 controls. Additionally, seven variants associated with ALS, two variants of unknown pathogenicity detected in ALS cases, eight mis-sense variants predicted to be damaging, and six rare variants were genotyped in these 259 ET cases and 262 controls.
Results
FUS/TLS mutations previously reported in ALS, the FET1 family, or novel mutations were not found in any of the 116 early-onset ET cases. In the case–control analyses, although the power of the performed associations was limited, no significant association between tagging SNPs in FUS/TLS and ET was observed, and none of the analyzed SNPs showed evidence of association with ET.
Conclusion
Our study suggests that pathogenic mutations in FUS/TLS are rare in a sample of early-onset ET cases in North America. We did not find evidence that the FUS/TLS gene is a risk factor for ET.
TL;DR: The discovery of several ALS genes strongly linked to RNA biology, the proteasome pathway, and axonal transport suggest they have an important role in pathogenesis, but the immense complexity of these processes is also apparent.
Abstract: The identification of genetic and epigenetic factors that are associated with an increased risk of developing amyotrophic lateral sclerosis (ALS), or that modify the age of onset or rate of progression, requires a multimodal research strategy, facilitated through international collaboration. The discovery of several ALS genes strongly linked to RNA biology, the proteasome pathway, and axonal transport suggest they have an important role in pathogenesis, but the immense complexity of these processes is also apparent. The increasing rate of genetic discoveries brings the hope of designing more targeted and efficacious therapies.